Fuel delivery systems may include a number of pumps, such as a lower pressure pump and a higher pressure pump in order to deliver fuel at a high pressure to the cylinders, such as for gasoline direct injection. Highly pressurized fuel in the fuel delivery system may be particularly useful during crank and other times during engine operation for efficient combustion, etc.
Leaks in the fuel delivery system may substantially decrease the fuel pressure in the fuel delivery system, thereby leading to extended crank times due to incomplete or inefficient combustion, for example. Extended crank times in turn may increase emissions and/or cause cylinder misfires.
In one example, U.S. Pat. No. 5,715,786 attempts to detect leaks in the fuel delivery system by monitoring the pressure in the fuel delivery system in response to a predeterminable operating state, such as overrunning. After a predeterminable operating state has been detected, the device assesses whether or not the fuel injectors have malfunctioned (i.e. whether an injector is stuck open and leaking fuel). A malfunction of one or more of the fuel injectors may be determined by comparing predeterminable pressure values to measured pressure values. The device may then take actions to mitigate fuel leak effects on the system, such as shutting down the engine or turning off the high pressure pump.
The inventor herein has recognized several disadvantages with this approach. First, internal and external leaks may not be differentiated in U.S. Pat. No. 5,715,786. An internal leak may include a fuel leak that occurs through various components in the fuel delivery system. For example, at high pressure during engine shut-down fuel may leak back through a pump, where the aforementioned leak can be classified as an internal leak. However, external leaks may include fuel leaks that leak out of various components in the fuel delivery system, exposing pressurized fuel to atmospheric pressure. For example, a fuel line may degrade and a hole may develop in a portion of the fuel line, substantially decreasing the pressure in the fuel delivery system and in some cases rendering the fuel delivery system inoperable, where the aforementioned type of leak can be classified as an external leak. An external leak may also include a leak through the fuel injectors.
One approach includes a method for operation of a fuel delivery system in an internal combustion engine including a lower pressure pump, a higher pressure pump fluidly coupled downstream of the lower pressure pump, and a fuel rail fluidly coupled downstream of the high pressure pump including, initiating a mitigating action based on a fuel rail pressure response, the fuel rail pressure response occurring after an engine shut-down, where the mitigating action includes disabling vehicle operation if fuel rail pressure drops below a threshold value after activation of one of the pumps, the activation occurring before a subsequent engine start, the subsequent engine start occurring after the engine shut-down, and where the mitigating action includes adjusting operation of one of the pumps during the subsequent engine start if fuel rail pressure achieves at least the threshold value during the activation.
Another approach includes a method for operation of a fuel delivery system in an internal combustion engine having a fuel system including a lower pressure pump, a higher pressure pump fluidly coupled downstream of the lower pressure pump, a solenoid valve coupled between the higher and lower pressure pumps, and a fuel rail fluidly coupled downstream of the high pressure pump comprising: indicating a fuel system leak based on a fuel rail pressure response, the fuel rail pressure response occurring after an engine shut-down; in response to the indication and before a subsequent engine start, the subsequent engine start occurring after the engine shut-down, adjusting the solenoid valve; differentiating whether the leak includes an internal or external leak based on fuel pressure response occurring after the solenoid valve is adjusted
In these ways, a distinction can be made between internal and external leaks, for example, allowing the mitigating action taken to be adjusted accordingly. In particular, the presence of either type of leak may be accurately obtained after an engine shutdown to reduce interference from engine operation. Then, different types of leaks may be accurately distinguished before a subsequent engine start due to the particular configuration of the system by monitoring the fuel rail pressure. Similarly, different types of leaks may be accurately distinguished by appropriate control of a valve in the fuel system that assists in isolating the leak source.